The present study investigates, numerically, the spill-return atomizer's (SRa) internal flow features within a 3D geometry by the use of a commercial code, ANSYS FLUENT. Experimental measurements, from the literature, are used to validate the numerical results of spray-cone angle (SCA), discharge coefficient (CD), and mass flow rates. The unsteady flow is solved as two-phase flow using the volume of fluid (VOF) method. The turbulence is captured using the K−ω shear-stress transport (SST) turbulence model. The geo-reconstruct scheme is used to capture the gas-liquid interface. An adaptive mesh refinement (AMR) is applied to refine the regions featuring high gradients in space. The simulations manage to capture the overall flow characteristics of a SRa with the formation of an air core and a thin liquid film in the exit region of the swirl chamber. Profiles of axial and tangential mean velocities are obtained. Furthermore, pressure measurements are conducted and pictures of the air core, velocity, and pressure field are taken for qualitative analysis. The tangential velocity profile resembles a Rankine vortex. The results show that air cores behave differently (size and shape) when changing the spill to feed ratio (SFR) due to a significant rise in the velocity profiles inside the swirl chamber, which directly affect the SRa performances, such as SCA and breakup process. The results show an important influence of the SFR variation on the gas-liquid volume fraction. A brief overview at the end is devoted to creation of the liquid spray cone outside of the injector, as well as the liquid sheet breakup process.

中文翻译：

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溢油返回雾化器的内部和近喷嘴瞬态流动

本研究通过使用商业代码 ANSYS FLUENT，在 3D 几何结构中以数值方式研究溢出返回雾化器 (SRa) 的内部流动特征。文献中的实验测量用于验证喷雾锥角 (SCA)、流量系数 (CD) 和质量流量的数值结果。使用流体体积 (VOF) 方法将不稳定流求解为两相流。使用 K−ω 剪切应力传输 (SST) 湍流模型捕获湍流。geo-reconstruct 方案用于捕获气液界面。应用自适应网格细化 (AMR) 来细化空间中具有高梯度的区域。通过在涡流室的出口区域形成气芯和薄液膜，模拟设法捕获了 SRa 的整体流动特性。获得了轴向和切向平均速度的分布。此外，还进行了压力测量，并拍摄了空气核心、速度和压力场的图片以进行定性分析。切向速度剖面类似于朗肯涡流。结果表明，由于涡流室内的速度分布显着增加，空气芯在改变溢流比 (SFR) 时表现不同（尺寸和形状），这直接影响 SRa 性能，例如 SCA 和破碎过程. 结果表明 SFR 变化对气液体积分数有重要影响。